Amazing end to one of (if not the) best series in Doctor Who (Classic included). Clara is one of my favourite companions (up there with Ace and Charley). Everything from the 8th series onwards has led to this. Her (toxic) relationship with the Doctor is given full focus in this episode, and the repercussions are enormous. The Doctor being cruel and cowardly is not out of character here, he is grieving and lets go of everything he believes in exchange for Clara's life. The episode calls him out on this, and, as he says at the end, he will make amends.

The 12th Doctor is my favourite just based on how much character development he gets throughout his 3 seasons. His era is so much fun to watch as you see him grow from a grumpy idiot to The Doctor (the definite article, you might say).